Abstract
Putnam (Representations and reality. MIT Press, Cambridge, 1988) and Searle (The rediscovery of the mind. MIT Press, Cambridge, 1992) famously argue that almost every physical system implements every finite computation. This universal implementation claim, if correct, puts at the risk of triviality certain functional and computational views of the mind. Several authors have offered theories of implementation that allegedly avoid the pitfalls of universal implementation. My aim in this paper is to suggest that these theories are still consistent with a weaker result, which is the nomological possibility of systems that simultaneously implement different complex automata. Elsewhere I (Shagrir in J Cogn Sci, 2012) argue that this simultaneous implementation result challenges a computational sufficiency thesis (articulated by Chalmers in J Cogn Sci, 2012). My focus here is on theories of implementation. After presenting the basic simultaneous implementation construction, I argue that these theories do not avoid the simultaneous implementation result. The conclusion is that the idea that the implementation of the right kind of automaton suffices for a possession of a mind is dubious.
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Notes
An early version (from the 1970s) of this argument is attributed to Ian Hinckfuss (see in Cleland 2002). Hinckfuss points out that under a suitable categorization of states, a bucket of water sitting in the sun (The "Hinckfuss' pail") can be taken to implement the functional organization of a human agent.
Minsky (1967) demonstrates the equivalence between these descriptions (the proof is on pp. 55-58; the gate-description is presented in terms of McCulloch and Pitts "cells").
Sprevak (2010) presents this result more elegantly without invoking tri-stable flip-detectors.
See also Scheutz (1999); for a related discussion see Melnyk (1996) and Godfrey-Smith (2009). Godfrey-Smith mainly addresses triviality arguments that group different types of physical states into one "implementing" type via disjunction. He thus suggests that the "substate variables map to independent parts of the realizing system", and that "the parts' microstates grouped into coarse-grained categories be physically similar" (2009: 292). I concur with these modifications, but they do not undermine my construction, which does not proceed through disjunctive grouping.
One could stipulate that minds are to be associated with characteristic automata but this condition is obviously ad hoc. This will entail that one loses her mind if some of her neurons turns out to be tri-stable rather than bi-stable.
Thus Chalmers (2012) writes: "It will be noted that nothing in my account of computation and implementation invokes any semantic considerations, such as the representational content of internal states. This is precisely as it should be: computations are specified syntactically, not semantically".
Godfrey-Smith (2009) distinguishes between a broad and a narrow construal of inputs and outputs.
This was suggested by Putnam (see the discussion in the “Putnam’s Argument” section). Godfrey-Smith (2009) advances an argument that aims to show that merely appealing to physical I/O does not block (other) triviality results.
There might be other physical properties that the robot metal arm and the biological human arm share; see Block(1978) for general discussion.
Something along these lines has been proposed by Scheutz (private communication).
It should be noted, however, that Piccinini does not aim to support CST. His proposal targets claims about individuation.
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Acknowledgments
I am grateful to Darren Abramson, Matthias Scheutz, Eli Dresner, Ilan Finkelstein, and three anonymous referees, for their comments, suggestions and corrections. The paper was presented in the Philosophy and Theory of Artificial Intelligence (PT-AI 2011) conference in Thessaloniki (October 2011). I am thankful to the participants for the lively and thorough discussion. This research was supported by The Israel Science Foundation, grant 1509/11.
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Shagrir, O. Computation, Implementation, Cognition. Minds & Machines 22, 137–148 (2012). https://doi.org/10.1007/s11023-012-9280-4
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DOI: https://doi.org/10.1007/s11023-012-9280-4